A theoretical framework has been developed for the "Laue" SAXS method, which makes use of broad-band quasi-white radiation. Because of an intensity increase of ~x10 relative to monochromatized beam, time-resolution of less than 1 msec may be expected for observing changes in R g of globular proteins. This technical improvement would help understand structure of transient folding intermediates such as the "molten globule". Calculations with simple models of the "white beam" (6-12 keV) show that the scattering patterns only start to deviate from the Guinier profile at angles where the Guinier approximation ceases to apply. When all beam line characteristics are included in the calculation, the scattering pattern with the "white beam" is essentially the same in the Guinier region as the monochromatized condition. Experimental evaluation of broad band-pass SAXS will be undertaken.